I am not entirely sure what to make a paper listed in this week’s Malaria World. Nor, indeed, are the authors. The title describes the content – ‘Small dams drive Anopheles abundance during the dry season in a high malaria burden area of Malawi’ by Zembere et al published in Medical and Veterinary Entomology. Its very unsurprising finding is that Anopheles mosquito larvae can develop in the shallow shores of the small reservoirs built with clay dams that the residents build to retain water from the rainy season for use in the dry season. Such dams are incredibly important in many parts of Africa to store water for people and their livestock.
This authors carry out a wonderful scientific study incorporating household surveys, indoor mosquito capture, drone image capture (a–d small dam and e–h close-up of an irrigation well and channels) and larval sampling to prove that there are more mosquitos in the dry season near where there are dams. There is no reference to malaria cases, even in the household survey.
The authors in their discussion write ‘What are the practical implications of our findings? Our investigation into the impact of small dams on mosquito populations and malaria transmission aims to inform recommendations for additional vector control that complement frontline tools like insecticide-treated nets. Based on our findings, small dam impoundments provide focal habitat for the most efficient malaria vector in Malawi, and targeting these areas with larval source management (LSM) could have substantial benefits for those communities living within their vicinity.’
The paper, which is mainly entomology, reminds me of Grassi’s research around 1900 that you can read about in my translation of ‘Studi di uno zoolologo sulla malaria’. The underlying assumption is that mosquitos spread malaria.
But what if mosquitos are not responsible for transmitting malaria? It is absolutely certain that water is essential for life and in dry regions of southern Africa dams such as those described in the paper are essential for life. Africa is the driest continent and in many parts conservation of limited water sources is essential. It is of no good if the local population is educated by researchers such as these from Wellcome and the Liverpool School of Tropical Medicine to unnecessarily fear their essential water sources.